Wood is a major source of fibers for paper production. The process of production of fibers from wood involves debarking raw logs. When high quality fibers are required, the logs must be reduced to chips for processing by cooking the wood fibers in a solution until the material holding the fibers together, lignin, is dissolved. In order to achieve rapid and uniform digestion by the cooking liqueur, the wood, after debarking, is passed through a log chipper which reduces the raw wood to chips.
The raw chips from the chipper contain many over-sized and grossly over-sized wood chips. In order to present chips of uniform thickness to the digesting liqueur, the over-sized and grossly over-sized chips are processed through a chip slicer which reduces the overall over-sized chips to chips of a uniform thickness.
A typical chip slicer has a housing with a fan-like rotor mounted inside. Chips are fed in at the hub of the rotor having radial anvil blades, and are thrown out against a rotating ring which supports a plurality knives located parallel to the axis of the rotation of the hub. The knife support ring rotates in the same direction as the hub, but not as rapidly, so that centrifugal force brings the chips out against the ring where the anvil blades sweep over the knives, forcing the over-sized chips against the knives, where they are cut or sliced to the required thickness.
Several problems exist with known chip slicers. One problem endemic to chip slicers is the undesirable production of fines and pins. Fines are wood particles so small as to contain no useful fiber; pins are wood particles containing some useful fiber, but of lower quality, so that the percentage of pins used to produce a paper pulp must be limited.
Another problem associated with existing slicers is the difficulty in adjusting the thickness of the chips produced. The normal solution requires the replacement of a gauge bar associated with each knife, and requires the unbolting, removal and replacement of the gauge bar to adjust chip thickness.
Yet another problem associated with known chip slicers is excessive wear on the knife holder clamps caused by abrasive movement of the chips and entrained dirt and sand over the clamp surfaces.
Yet another problem associated with known chip slicers is that the blades become dull and must be periodically replaced. The down-time associated with blade removal can be excessive in some cases.
What is needed is a chip slicer which produces fewer fines and pins, and which is readily adjustable to form chips of varying thicknesses. Also desirable are chips slicers with more rapid change-out of slicer knives.